1. Field of the Invention
The present invention pertains to furniture, such as tables, chairs, bureaus, chests, etc. having at least four legs, which furniture would, in the absence of the invention, have a tendency to wobble or rock when placed on an uneven surface.
2. Description of the Prior Art
The problem of wobbling furniture has been recognized for a long time and various means of countering such rocking have been proposed in the patent literature. However, none of these inventions seem to have resulted in significant commercial manufacture of non-wobbling furniture because either the proposed means were not effective, too cumbersome, or complicated and expensive to fabricate. It has generally been recognized, that to make furniture with four or more legs wobble-resistant, at least two legs need to be modified. If only one leg is modified, it has to be one of the wobbling pair, and the only way to ensure this is to make one leg shorter than the other legs, but with a length-adjusting insert, as in the table disclosed in U.S. Pat. No. 1,826,578. However, after the length of the adjustable leg has been secured for one floor location of the table, it must be readjusted any time the table is moved to a different floor location where all four legs do not touch the ground. If the extension of the modified leg is automatic, by making it spring-loaded as shown in U.S. Pat. No. 3,827,663, the spring must be carefully adjusted to make it strong enough to prevent wobbling of the modified leg with its opposite leg, yet not so strong that it will lift its side of the table and cause wobbling between the other two legs. It has therefore been recognized that self-adjusting wobble-resistant furniture generally requires modification of at least two legs. The earliest patents on wobble-resistant furniture involve modification of two adjacent legs. For example, U.S. Pat. Nos. 467,811 and 520,432 to W. J. Humphreys describe means to connect adjacent legs of four-legged furniture in such a way that as one leg moves down the other moves upward to correct any wobbling caused by one of these legs initially not touching the ground. In these and numerous later patents based on the same principle, the interaction of the adjacent legs is achieved by various mechanical, hydraulic or electronic means which make such furniture expensive to construct and maintain. The same can be said of wobble-resistant furniture involving modification of two or more non-adjacent legs in such a way that there is a connection between these legs for mutual length adjustment. If there is no connection between the movement of the legs, separate manual adjustments are usually required. For example, U.S. Pat. No. 1,224,156 describes a table leg leveler where two or more legs have inserts connected to springs and provided with releasable ratchets to hold the legs extended to the ground. Manual adjustment of the length of each adjustable leg that does not touch the floor is required to prevent the table from wobbling. In the description of wobble-resistant furniture in U.S. Pat. No. 2,204,077, gravity is mentioned as a force to extend an adjustable leg under the weight of its insert, which by itself does not adequately stabilize the table.